Method of making hypodermic needles and like articles



Nov. 28, 196.1 .1. K. ROEHR 3,010,197

METHOD OF MAKING HYPODERMIC NEEDLES AND LIKE ARTICLES FiledJan. so, 1958INVENTOR w/ ATTORNEYS United States Patent C 3,010,197 METHQD OF MAKINGHYPODERMIC NEEDLES AND LIKE ARTICLES Jan Kanty Roehr, Waterbury, Conn.,assignor to Roehr Engineering Company, Waterbury, Conn., a limitedpartnership Filed Jan. 30, 1958, Ser. No. 712,226 3 Claims. (Ci. 29-423)This invention relates to a method of making hypodermic needles and likearticles having a tubular stem or cannula of small diameter formed ofstainless steel or similar material.

In making cannulas for hypodermic needles, the present practice is todraw stainless steel tubing stepwise down to the required diameter whichis achieved after a long tube has been cut into a plurality of shorterlengths. From a coil of tubular wire, lengths of, say, eight feet arecut and a mandrel in the form of a metal rod is inserted into thetubelength and then each length is drawn down upon and with the mandrelto reduce the diameter. Sometimes this drawing-of the mandrel-carryingtube was performed more than oncegand, at other times there was only onedrawing which wasfollowed by further reduction of diameter without amandrel, which operation is known as sinking. In connection with suchoperations the tube is annealed and the reduction is continued until avery fine hollow tube is produced having the diameter desired for thefinished cannula. After the first drawing operation, the mandrel, overwhich the wire is drawn, must be removed for if this were done at alater stage with its incident length of wire there would be greatdifiiculty in removing the mandrel. Also the first drawing operation oroperations will very greatly increase the length of the wire that was inthe original coil, making it very difiicult to handle. For these reasonsthe operation of drawing the original wire down to cannula diameter hasnot been a continuous one.

One of the objects of the present invention is to provide a process bywhich the reduction of the initial tubing to the diameter of thefinished product, such as a needle cannula or other fine tube, can beperformed in a continuous process or substantially continuous processwith the elimination of the need for shortening the wire length inpreparation for a subsequent drawing step or steps.

A further object is to cheapen the process of making cannulas and likearticles and to expedite the production of such articles from tubularmaterial that can be obtained in coils of any desired length.

To these and other ends the invention consists in the process and thesequence of steps as hereinafter described and defined in the claims.

In the accompanying drawing:

FIG. 1 is an enlarged longitudinal section of a hypodermic needle;

FIG. 2 is an enlarged longitudinal section of a portion of a length oftubular wire encasing a tubular mandrel;

FIG. 3 is a section on line 33 of FIG. 2;

FIG. 4 is a view similar to FIG. 2 showing the mandrelsupported tube ata later stage in the process;

FIG. 5 is an enlarged longitudinal section of a further reducedmandrel-supported tube cut to the length of the finished article; and

FIG. 6 is a view similar to FIG. 5 showing one end portion in elevation.

In FIG. 1, a hypodermic needle is shown having a tubular stem or cannula10 sharpened at one end and threaded at the other end for connectionwith the customary handling piece or hub 11. At its rear end the cannulais provided with threads 12 engaging internal threads for exampleseveral hundred feet, may be used as an outer' element to be drawn 'upona mandrel, the mandrel being a wire of soft carbon steel and preferablya tubular wire of such steel. The mandrel-supported tube will be ofsufiicient length for the manufacture of a multiplicity ofsmall-diametered short tubes such as cannulas. FIG;

2 shows a portion of the original outer wire after it has been drawndown to an extent upon the tubular mandrel. In this view the outer tubeis shown at 15 and the mandrel at 16. The outertube 15 may be formed ofwelded strip and the mandrel may be formed from welded strip. In FIG. 3the welds of the tubes are indicated, but it may be pointed out herethat so far as the mandrel is concerned, this may be in the form of atubular strip having abutting edge portions and lacking a weld.

FIG. 4 shows the assembly of FIG. 2 after an additional drawing step hasbeen performed, lengthening to an additional extent the tubular article.Between the drawing operations annealing may be effected in theusual-manner. The number of draws may be varied as required by theexisting conditions but it may be assumed, for example, that followingthe first draw resulting in the article of FIG. 2, the second drawresulting in the article of FIG. 4, and a third draw reducing thearticle to the extent shown in FIG. 5 (which is another much enlargedview), there is no further drawing. There is, however, a straighteningof the composite tube comprising the inner and outer members which maybe done by means of straightening rollers in a manner well known in theart. The next step is to cut the tube to lengths corresponding to thatof the finished cannula, this being done by a suitable cutting device.In practice the cannula may have a length somewhat in excess of one andone-half inches, for example, and FIG. 5 shows a considerableenlargement. At this stage the ends of the blank are honed so that aftercutting the ends are smooth. The next step is to provide means forconnecting the can nula to the hub, and for this purpose the threads 12are 7 formed by rolling one end of the blank. The blank is then in thecondition shown in FIG. 6. Instead of forming threads upon the outertube (FIG. 6) parallel ribs may be rolled upon the blank so that at alater stage the hub of the needle may be forced over such ribs to holdthe hub on the cannula. The cannula is preferably sharpened before themandrel is removed.

The next step is to remove the mandrel or core from the article shown inFIG. 6 and this may be done by a mechanical means or by a chemicalprocess. If this is done chemically, the article is subjected to theaction of a strong acid which will dissolve the core without injuringthe outer tube. A suitable acid for this purpose is nitric acid and theprocedure preferred is the boiling of the article in a bath of nitricacid, for example, which will dissolve the core and remove it from theouter tube. It is then advisable to clean the outer tube to remove anydiscoloration which may have resulted from the bath. After thistreatment the distal end of the cannula is sharpened in the usual or anypreferred manner.

While in the foregoing description the outer tube carrying the mandrelis subjected to three drawing operations, the results of which are shownin FIGS. 2, 4 and 5, which operations take place upon the workpiecebefore cutting the workpiece to divide it into sections, the number ofPatented Nov. 28, 1961 cannula assists in straightening thecorresponding end of the tube.

The soft carbon steel wire used as a core or mandrel may be, in somecases, a solid wire rather than a tubular one. geous. The use of a solidWire requires a rather heavy outer stainless steel tube (provided with arather thick wall.) since the reduction in the wall thickness duringeach drawing pass is considerable. Where a tubular mandrel or core isused, as described above, made from carbon steel or any other suitablesoft material, the resistance of the core is reduced and this permitsless reduction of the outer wall during each drawing pass. Due to this,standard sizes of stainless steel tubing can be used as the initialmaterial with considerable savings in time and expense. I

Among materials suitable for use in providing an inner core are plasticmaterials.

Instead of beginning the operation by drawing a mandrel-supported tubeit may be begun with a small tape of stainless steel having the mandrelor core laid thereon. The tape may then be formed up around the mandreland welded. This will be a preliminary step producing the same rawmaterial with the core inside which Was mentioned above.

Various changes in the detailed procedure herein described may be madewithout departure from the principles of the invention and the Scope ofthe claims.

However, the use of a tube as a core is advanta What I claim is:

l. The method of making small tubular metal articles such as cannulas,which method comprises providing stainless steel tubing supported uponan interior tubular mandrel and of a length suitable for-the manufacturetherefrom of a multiplicity of small tubes, said mandrel be ing ofsofter material than the outer tubing, drawing this assembly orcomposite workpiece a number of times to reduce its diameterprogressively while the workpiece is continuous, then, after the outertubing has been reduced to the diameter desired in the finished article,cutting the tubing and mandrel into sections corresponding substantiallyto the desired length of the finished article, then sharpening one endof each of said sections and rolling the other end of each of saidsections to provide projections upon the outer tubing engageable with aneedle hub, and then removing the mandrel portions from the cut-ottsections.

2. The method of claim 1 in which the mandrel portions are removed bychemical treatment.

3. The method of claim 1 in which the mandrel portions are removed bydissolving them in an acid solvent.

References Cited in the file of this patent UNITED STATES PATENTS1,568,369 Everett Jan. 5, 1920 1,891,304 Everett Dec. 20, 1932 1,913,206Littler June 6, 1933 2,022,234 Everett Nov. 26, 1935 2,047,555 GardnerJuly 14, 1936 2,800,942 Parker et al. July 30, 1957 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3,010,197 November 28, .1961

Jan Kanty Roehr It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

In the grant, lines 2 and 3, for "assignor to Roehr Engineering Company,of Waterbury, Connecticut, a limited partnership," read assignor, bymesne assignments, to Brunswick Corporation, of Chicago, Illinois, acorporation of Delaware, line 12, for "Roehr Engineering Company, theirheirs" read Brunswick Corporation, its successors in the heading to theprintedspecification, lines 4 to 6, for "assignor to Roehr EngineeringCompany, Waterbury, Conn.,

a limited partnership" read assignor, by mesne assignments to BrunswickCorporation, Chicago, Ill. a corporation of Delaware,-.

Signed and sealed this 19th day of March 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD' Attesting Officer Commissioner ofPatents

